1. Field of the Invention
The present invention relates to a method and program for estimating uncertainty of measuring machines such as a CMM (Coordinate Measuring Machine) and others.
2. Description of the Related Art
In general, uncertainty of measuring machines can be computed by identifying all error factors and synthesizing them in consideration of error propagation. Uncertainty analysis by such the theoretical computation can be relatively easier to execute when a measuring system is simple and its uncertainty can be determined in a single way while it becomes very difficult as the system is complicated.
For example, measurement by a three-dimensional measuring machine is executed in accordance with an arbitrary measurement strategy (such as the number of measurement points, and measurement positions), and the shape is evaluated as various parameters (such as roundness, flatness and perpendicularity) through further complicated arithmetic processing. In such the complicated measurement, it is practically impossible for the theoretical error analysis to estimate uncertainty.
Methods of estimating the theoretical analysis-hard uncertainty include those currently growing into the mainstream, which employ the Monte Carlo technology. Among those, a method with the highest completion is the Virtual CMM method proposed by PTB (German Metrology Institute) et al. (“Traceability of coordinate measurements according to the method of the virtual measuring machine”, PTB-Bericht, MAT1-CT94.0076, (1999)). The Virtual CMM method comprises forming a pseudo-three-dimensional measuring machine on a computer, and using the measuring machine to simulate measurement for estimation of uncertainty of the measuring machine. Initially, error factors in the three-dimensional measuring machine, the probe, and the environments are identified, and the magnitudes thereof are estimated through a preliminary measurement. These errors are multiplied by random numbers for swinging to generate pseudo-errors. The preliminary measurement, however, requires several days, which impose a considerably heavy burden on the user.